Java基础之处理事件——applet中语义事件的处理（Lottery 1）

控制台程序。

语义事件与程序GUI上的组件操作有关。例如，如果选择菜单项或单击按钮，就会生成语义事件。

对组件执行操作时，例如选择菜单项或单击按钮，就会生成ActionEvent事件。在选择或取消选择某个组件时，会生成ItemEvent事件。在调整可调整的对象(如滚动条）时，就生成AdjustmentEvent事件。

上面的每一种语义事件类型都定义了相应的监听器接口，这些接口都只声明了一个方法：

1、ActionListener定义了actionPerformed(ActionEvent e)方法。

2、ItemListener定义了itemStateChanged(ItemEvent e)方法。

3、AdjustmentListener定义了adjustmentValueChanged(AdjustmentEvent e)方法。

// Applet to generate lottery entries
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.util.Random;                                               // For random number generator

@SuppressWarnings("serial")
public class Lottery extends JApplet {
  // Generate NUMBER_COUNT random selections from the VALUES array
  private static int[] getNumbers() {
    int[] numbers = new int[NUMBER_COUNT];                             // Store for the numbers to be returned
    int candidate = 0;                                                 // Stores a candidate selection
    for(int i = 0; i < NUMBER_COUNT; ++i) {                            // Loop to find the selections

      search:
      // Loop to find a new selection different from any found so far
      while(true) {
        candidate = VALUES[choice.nextInt(VALUES.length)];
        for(int j = 0 ; j < i ; ++j) {                                 // Check against existing selections
          if(candidate==numbers[j]) {                                  // If it is the same
            continue search;                                           // get another random selection
          }
        }
        numbers[i] = candidate;                                        // Store the selection in numbers array
        break;                                                         // and go to find the next
      }
    }
    return numbers;                                                    // Return the selections
  }

  // Initialize the applet
  @Override
  public void init() {
    SwingUtilities.invokeLater(                                        // Create interface components
      new Runnable() {                                                 // on the event dispatching thread
        public void run() {
          createGUI();
        }
    });
  }

  // Create User Interface for applet
  public void createGUI() {
    // Set up the selection buttons
    Container content = getContentPane();
    content.setLayout(new GridLayout(0,1));                            // Set the layout for the applet

    // Set up the panel to hold the lucky number buttons
    JPanel buttonPane = new JPanel();                                  // Add the pane containing numbers

    // Let's have a fancy panel border
    buttonPane.setBorder(BorderFactory.createTitledBorder(
                         BorderFactory.createEtchedBorder(Color.cyan,
                                                          Color.blue),
                                                          "Every One a Winner!"));

    int[] choices = getNumbers();                                      // Get initial set of numbers
    for(int i = 0 ; i < NUMBER_COUNT ; ++i) {
     luckyNumbers[i] = new Selection(choices[i]);
     luckyNumbers[i].addActionListener(luckyNumbers[i]);               // Button is it's own listener
     buttonPane.add(luckyNumbers[i]);
    }
    content.add(buttonPane);

    // Add the pane containing control buttons
   JPanel controlPane = new JPanel(new FlowLayout(FlowLayout.CENTER, 5, 10));

    // Add the two control buttons
    JButton button;                                                    // A button variable
    Dimension buttonSize = new Dimension(100,20);                      // Button size

    controlPane.add(button = new JButton("Lucky Numbers!"));
    button.setBorder(BorderFactory.createRaisedBevelBorder());
    button.addActionListener(new HandleControlButton(PICK_LUCKY_NUMBERS));
    button.setPreferredSize(buttonSize);

    controlPane.add(button = new JButton("Color"));
    button.setBorder(BorderFactory.createRaisedBevelBorder());
    button.addActionListener(new HandleControlButton(COLOR));
    button.setPreferredSize(buttonSize);

    content.add(controlPane);
  }

  // Class defining custom buttons showing lottery selection
  private class Selection extends JButton implements ActionListener {
    // Constructor
    public Selection(int value) {
      super(Integer.toString(value));                                  // Call base constructor and set the label
      this.value = value;                                              // Save the value
      setBackground(startColor);
      setBorder(BorderFactory.createRaisedBevelBorder());              // Add button border
      setPreferredSize(new Dimension(80,20));
    }

    // Handle selection button event
    public void actionPerformed(ActionEvent e) {
      // Change this selection to a new selection
      int candidate = 0;
      while(true) {                                                    // Loop to find a different selection
        candidate = VALUES[choice.nextInt(VALUES.length)];
        if(!isCurrentSelection(candidate)) {                           // If it is different
          break;                                                       // end the loop
        }
      }
      setValue(candidate);                                             // We have one so set the button value
    }
    // Set the value for the selection
    public void setValue(int value) {
      setText(Integer.toString(value));                                // Set value as the button label
      this.value = value;                                              // Save the value
    }

    // Check the value for the selection
    boolean hasValue(int possible) {
      return value==possible;                                          // Return true if equals current value
    }

    // Check the current choices
    boolean isCurrentSelection(int possible) {
      for(int i = 0 ; i < NUMBER_COUNT ; ++i) {                        // For each button
        if(luckyNumbers[i].hasValue(possible)) {                       // check against possible
          return true;                                                 // Return true for any =
        }
      }
      return false;                                                    // Otherwise return false
    }

    private int value;                                                 // Value for the selection button
  }

  // Class defining a handler for a control button
  private class HandleControlButton implements ActionListener {
    // Constructor
    public HandleControlButton(int buttonID) {
      this.buttonID = buttonID;                                        // Store the button ID
    }

    // Handle button click
    public void actionPerformed(ActionEvent e) {
      switch(buttonID) {
        case PICK_LUCKY_NUMBERS:
          int[] numbers = getNumbers();                                // Get maxCount random numbers
          for(int i = 0; i < NUMBER_COUNT; ++i) {
            luckyNumbers[i].setValue(numbers[i]);                      // Set the button VALUES
          }
          break;
        case COLOR:
          Color color = new Color(
                flipColor.getRGB()^luckyNumbers[0].getBackground().getRGB());
          for(int i = 0; i < NUMBER_COUNT; ++i)
            luckyNumbers[i].setBackground(color);                      // Set the button colors
          break;
      }
    }

    private int buttonID;
  }

  final static int NUMBER_COUNT = 6;                                   // Number of lucky numbers
  final static int MIN_VALUE = 1;                                      // Minimum in range
  final static int MAX_VALUE = 49;                                     // Maximum in range
  final static int[] VALUES = new int[MAX_VALUE-MIN_VALUE+1];          // Array of possible VALUES
  static {                                                             // Initialize array
    for(int i = 0 ; i < VALUES.length ; ++i)
      VALUES[i] = i + MIN_VALUE;
  }

  // An array of custom buttons for the selected numbers
  private Selection[] luckyNumbers = new Selection[NUMBER_COUNT];
  final public static int PICK_LUCKY_NUMBERS = 1;                      // Select button ID
  final public static int COLOR = 2;                                   // Color button ID

  // swap colors
  Color flipColor = new Color(Color.YELLOW.getRGB()^Color.RED.getRGB());

  Color startColor = Color.YELLOW;                                     // start color

  private static Random choice = new Random();                         // Random number generator
}

还需要一个HTML文件：

<html>
    <head>
    </head>
    <body bgcolor="000000">
        <center>
            <applet
                code    = "Lottery.class"
                width    = "300"
                height    = "200"
                >
            </applet>
        </center>
    </body>
</html>